EN
The effect of the amino acids l-cysteine (CYS-SH), l-aspartic acid (ASP-OH) and l-glutamic acid (GLU-OH), and of polycarboxylic acids (PCAs) on the biological activity of co-balt in cultures of Scenedesmus armatus (Chodat) and Synechocystis aquatilis (Sauvageau) was investigated. The influence of metal ions was determined by measurements of chlorophyll a content in the cultures and rates of carbon fixation by the phytoplankton cells. The addition of cobalt (2.5*10-6 M) to the cultures caused inhibition of growth, monitored by the chlorophyll a concentration and the photosynthetic rate of both green algae and cyano-bacteria. It was found that these acids significantly increased the chlorophyll a content in both algal species when treated with cobalt. Polycarboxylates, CYS-SH and ASP-OH also increased the rate of C-14 incorporation into algal cells in both cultures, whereas GLU-OH was effective in cultures of Synechocystis only.The results indicate that organic compounds, polycarboxylates and amino acids modify the biological activity of the cobalt. The environmental consequences of these processes are considered.